Electric motor



Feb. 18, 1941. w. T. BRENNAN v 2,232,363

ELECTRIC MOTOR Qriginal Filed May 30, 1938 I9 Fig.1 4 5 5 55 59 41 4a 523; 5O 44 4a 4/ B49 52 ul 5 54 46 A 4 27 56 33 Z3) 55 5! h 3 24 57 53 5/55 Z5 Z4 52. 5

41 49 ao g gg 56 40 45 INVENTOR WILLIAM T. BRENNAN adam ATTORNEYPatented Feb. 18, 1941 assess: nnno'rmc Moron William T. Brennan,Dunmore, Pm, assignor to I Scranton Electric Toothbrush Corporation,

Scranton, Pa.

application May so, less, Serial No. 208,960. Divided and thisapplication May 9.

1939, Serial No. 212,671

8 Claims.

This invention relates to an improved electric motor of the magnetictype which operates on a make-and-break principle. The motor is adaptedfor any use but is particularly adapted i for use in small hand toolssuch as a rotary tooth brush andthe Motors operating on themake-and-break principle, suchasused'in dry-shavers, are light in weightbut heretofore have generally rotated 10 only in one direction. Motorsof this type, heretoforegenerally used, are usually provided with a camfixed on the motor shaft or part of the motor shaft. The cam is usuallyarranged to open the make-and-break points a short time it before thecenter line of the rotorpoles becomes colinear with the center line ofthe field poles and to maintain the pointsin this open position untilthe center line of the rotor poles has rotated a considerable distancebeyond the point 20 where it was colinear with" the center line of the"ileld poles, at, which point the cam allows the make-and-break contactsto close. In a twopole motor this operation normally occurs twice inevery revolution, and a motor so built will 26 rotate only in onedirection. After once being iven a start a motor so constructedwillrotate in a direction fromjth'e point where the rotor is whenthejeontacts are-opened. through the arc during which thelcontactssre.held open.

' i so t a point wn'erethe mm is when the are ciosed.-- Theunidirectional feiture of, makeand-break type motors, which haveheretofore been used has made them generally unsatisfactory for use withmotor-driven rotary tooth 88 brushes.

This invention contemplates the provision of a new light weight motorwhich operates on the make-and-break principle and which may be easilyand emciently reversed.

so A further obiectof this invention is to Provide a reversible motor ofthe magnetic attraction type operating on a make-and-break circuit, suchas, for example, those employed in actuat ing the moving parts of rotarytooth brushes or v In accordance with this invention in one form thereofa motor of the magnetic attraction type is provided with cam surfaceswhich are turnably mounted with respect to the main motor shaft. 5

For a more complete understanding of this invention, references shouldbe had to the accompanying drawing in which:

Figure l' is a plan view of the motor installed in a small housing unit.The cover is not shown, 10 thus this figure shows the internalmechanism,

Figure 2 is a perspective view of parts 'of the motors, main shaft andsome of the associated mechanisms,

Figure 3 is a fragmentary cross-section ll through the motor duringclockwise rotation of Figure 5 is a cross-section view on the line 255-! of Figure 1, partly broken away to show a high-cam surface at theinstant it starts to open the contacts of themake-and-break device dur-I in: counter-clockwise rotation, I

Figure- 8 is a fragmentary cross-section so ,through the motor duringcounter-clockwise rotation, broken away to show a high cam sur-' face atthe point where it allows the make-andbreak device to close.

Referring to the drawing, this invention has as been shown in one formas applied to a small motor unit adapted for use in small hand toolssuch as a rotary tooth brush and the like. This unit comprises smallhigh speedmotor ll housed in a handle member ll preferably of "Bakelite"0 or the like. For convenience in describing the device the portionfarthest to the left in Figure 1 will be referred to as "back, while theportion to the right will be referred to as front."

. The motor comprises a field magnet 28 which 45 is madev with an openend providing opposite poles 2| and il. The field magnet which isPreferably made of laminated sheets riveted together, is approximatelyU-shaped and the crossarm or reach is provided with the coil 20. The socenter line of field poles is shown at 21.

p The rotor It is not wound and is arranged within the field magnet andpositioned between the ends or field poles and ii. The rotor is I madeof laminated sheets riveted together and sg 2. aaaasss has two oppositeconvex ends or poles fl and II, the opposite sides 3| of the rotorbetween the poles being cut away in a manner well-known to the art. Thecenter line through rotor poles is shown at 32. The rotor 28 preferablyrevolves in a plane perpendicular to the plane of the fleld magnet andis supported on main shaft 83 and is securely fastened preferably bymeans of a set' screw to main shaft 33 which is rotatably supported atthe back in a bearing 34. At the front end, shaft 33 is rotatable in andsupported by bearing 34. The bearings 34 and II are rigidly supported bythe non-metallic frame I! which is rigidly supported in handle ll.

One terminal 38 mounted in insulated handle I! is electrically connectedto one side of coil 28 by conductor 39. The other side of the coil isconnected to the make-and-break device 4| by means)! conductor 4i. Theother side of the make-and-brealr. de ice is connected to the remainingterminal 4! by means of conductor 43. Terminal 42 is also mounted oninsulated handle IS. The make-and-break device 4|, for turning on andshutting off the current in coil 26 and thus the magnetic flux infieldmagnet 13, consists of two contact points 44 and 4|. Point 44 isstationary and is semi-rigidly mounted on insulated frame 31, beingadjustable only by the movement of bolt 46 or by some other suitablemeans. Point 45 is movable, since it is mounted on one end of flexiblearm 41. The other end of flexible arm 41 is rigidly fastened to frame 81as described below. Disposed above and in contact with flexible arm 41is leaf-spring 48. Leafspring 48 supplies pressure to flexible arm 41 insuch a manner as normally to hold movable point 45 in contact withstationary point 44. Leafspring 48 and flexible arm 41 are clampedtogether and fastened to the frame I! by bolt 49. Disposed below andriveted t0 flexible arm 41 is an insulating member which acts as camfollower 50.

Swivel 5i, preferably in the form of a cylindrical collar, is looselymounted coaxially on main shaft 33 and is longitudinally positioned infront of bearing 34. The portion of swivel 5| disposed belowmake-and-break device 44 acts as a cam and has opposite sides cut awayto provide voids which act as low surfaces 52, leaving the uncutawayportions to act as high surfaces 53 and 54 of the cam. It should benoted that I have chosen to show two high cam surfaces It and 54 for usewith my bi-polar motor. These high cam surfaces are spaced 180 apart onopposite sides of the swivel II. The edges of these high cam surfacesare rounded off to insure that they operate smoothly when they engagecam follower 5|. It should also be noted that-40w cam surface 52 and thehigh cam surfaces 53 and I4 combine to form an approximately ellipticalshaped cam. The main shaft 33, swivel ii, and make-and-break device 4|are positioned in spaced relationship one with the other so that thefollowing will be accomplished: flrst, when either one of the voids 52is beneath insulating cam follower I, spring 4! will cause points 44 and4! to make contact and thus completes the electric circuit through coil24. Second, when either of the cams high surfaces It or 54 are rotatedso as to approach the point where they will be directly under the camfollower N, the high cam surface will make contact with cam follower lland will start to open the contact points 44-- 4li. Third. when theabove mentioned high cam surface has once opened the points '44-, thehigh cam sub face will maintain the points "-45 in the open positionuntil the high cam surface has passed well beyond the point where thehigh cam surface was directly under the cam follower II. In other words,swivel ll provides the necessary cam action required to raise and lowerflexible arm 41 and thus opens and closes contacts "-0.

The front end of swivel II is provided with notch ll, preferably in theform of a sector cut out of the cylindrical walls of the swivel. Pin llextends radially from shaft 83 and is preferably fastened to shaft 33 byscrew threaded engagement. Pin I is positioned within notch II and isthe sole restraining member which keeps swivel ll from rotating freelyon shaft 33. It should be noted in Figure 4 that pin It cannot move outof notch II in a direction longitudinal with the shaft. The rotor 28 isfixed to the shaft 33 directly in back of bearing 34 and the swivel IIis located directly in front of bearing 84, the pin 54 being fastened toshaft 30 in notch ll so as to maintain this relationship.

It has been desirable to provide swivel ii which acts as anautomatically adjustable cam. If the shaft 33 is rotated in theclockwise direction as viewed from the front, then shaft 33 causes pin56 to take a position in notch I! as at 51, and swivel ll follows shaft:1 in its clockwise rota tion as viewed from the front. If the shaft 88is rotated in a counter-clockwise direction as viewed from the front,the movement of the shaft causes pin II to take a position in the notchI. as at I and swivel ll follows shaft 88 in its counterclockwiserotation. This movement of swivel II on shaft 33 causes the cams highsurfaces It and 84 to assume with respect to the center line of therotor poles 32 a different position for clockwise than forcounter-clockwise rotation of shaft ll. It is desirable to speak ofswivel I as being swivelly mounted on shaft ll, or swivel ll as shown inthis preferred embodiment might be termed a collar means turnablymounted for a limited lost motion on shaft I3. It should be noted thatsince the rotor 28 and pin N are both rigidly fastened to shaft 33, therotor II has a flxed relationship with respect to pin ll. Also the camshigh surfaces I and 54, as well as notch 55 are both parts of the sameswivel II, and thus high surfaces '3 and 54 have a fixed relationshipwith respect to notch ll.

I have chosen to show pin "as having its axis perpendicular to thecenter line of the rotor poles 31. I have also chosen to show the highcam surface 53 as being positioned so'that the center line of camsurface will bisect the seetoral segment or notch I5. I have chosen toshow sectoral notch 55 as having a central angle of approximately 90although this angle may be varied considerably depending. on thediameter of pin 58 and other dimensions.

I have chosen to show starting wheel ll positioned directly in front ofswivel 5|. This wheel is coaxlally mounted on main shaft is and is fixedthereto by means of set screw 6|. when the cover (not shown) is in placethe starting wheel 5! projects through a slot (not shown) in the cover(not shown) so that enough of the wheel projects to allow it to bestarted in either direction by a sweep of the finger, and to be stoppedby pressure of the finger. The wheel 58 is the means provided forstarting or stopping the motor and is the only means provided forreversing the direction of rotation of the motor.

In the operation of this apparatus, if it is de- 2,a'ss,ses

42 are connected by a suitableextension cord' (not shown) to a suitablesource of electric power supply. I The over starting wheel ll in eitherdirection depending on which wayit is desirable to have the motorrotate. If the starting wheel" is turned in a clockwise direction asviewed from the front end, starting wheel II will rotateshaftfl in aclockwise direction. Thiswillcausepinll toassumeaposition in notchll asshown at 'I (see Figures 3 and 4). Pin It then causes swivel II to turnin a clockwise direction which inturn causes high cam surfaces "and I4to rotate in a clockwise direction. When one. of the high cam surfacesenases cam follower "(see Figure 3) flexible arm 41 is caused to liftagainst the pressure of springs 48. The lifting of arm 41 opens contacts"-45. As the swivel is rotated, the high cam surface finally passesbeyond cam follower I. (see Figure 4) and allows cam follower II,flexible arm 41, and spring ll to assume their normal positions, thusclosing contacts "-0. The closing of contacts 44- causes coil 26 to beenergized which in turn causes the rotor 20 and shaft It to be rotatedin a manner well-known to the art.

If it is desirable to stop the motor II, the finger is pressed heavilyonto wheel it until the motor stops or the electrical service connectionmay be opened and held open.

If it is desirable to rotate the motor is in,

the counter-clockwise direction (see Figures 5 and 6), the startingwheel 5! is turned in the counter-clockwise direction and the startinlwheel I. will rotate shaft 33 in a counter-clockwise direction. Thiswill cause pin '0 to assume a position in notch ll as shown at I. Pin Itthen causes swivel II to rotate in the counterclockwise direction, whichin turn causes high cam surfaces II and 54 to rotate in acounterclockwise direction. When one of the high cam surfaces engagescam follower it (see Figure 5), the contacts "-4! are opened and laterthe cam surfaces allow points "-4! to close (see Figure 6), in a mannersimiliar to that previously described for clockwise rotation. The motornow by angle "A" (see Figures 3 and 5). It should also be noted thatregardless of the direction of rotation of shaft 88, the uncutaway camsurfaces IS or II maintain the contacts "-48 in the open position untilthe center line of rotor poles 82 has passed well beyond the point whereit was colinear with the center line of field poles 21 as shown by angle3" (see Figures 4 and 8). This operation is accomplished by pin llshifting from position 51 to position It or vice versa in notch 55,depending on the direction of rotation of shaft 38. Another way ofexpressing this same idea is to say that the high carn surfaces It and Iassume a different relative position with respect to the center linethrough rotor poles 32 for clockwise rotation than for counter-clockwiserotation because swivel ll is swivelly mounted on shaft II.

It has been found that a motor constructed in accordance with thisinvention will operate satisfactorily in either direction when connectedto either direct-current or alternating-current circuits, and that ifthe motor is connected to a proper power source and started in aclockwise direction, it will satisfactorily operate in that directionuntil stopped, and that if the motor is connected to a proper powersource and started in a counter-clockwise direction, it willsatisfactorily operate in that directionuntil stopped.

It is to be understood that the form of the invention, herewith shownand described, is to be taken as a preferred example of the invention,and that various changes in the shape, size, arrangement of parts, andother details may be resorted to, without departing from-the spirit ofthis invention. or the scope of the su-bioined claims.

What I claim as new and desire to secure by Letters Patent 01' theUnited States is:

1. A reversible electric motor of the magnetic attraction typehaving asits reversing mechanism a make-and-break device, a collar means mountedon the shaft of said motor, means on said collar means for operatingsaid make-andbreak device, and a means for limiting the motion of saidcollar means with respect to said shaft.

2. A reversible electric motor comprising field poles, coil means formagnetizing said field poles, a main shaft, rotor poles fixed to saidshaft and rotatabiy positioned between said fleld poles, amake-and-break device for alternately energizing and deenergizing saidcoil means, and cam surfaces for opening and closing said make-andbreakdevice, said cam surfaces being mounted for a limited lost motion withrespect to said rotor poles.

8. An electric motor of the magnetic attraction type having as itsreversing mechanism a make-and-break device, a shaft, a collarmeansturnable with respect to said shaft, means on said collar means foroperating said make-andbreak device, and a means for limiting the motionof said collar means with respect to said shaft. a

4. A reversibleelectric motor of the magnetic attraction type having asits reversing means a device comprising amake-and-break means, a shaft,and a cam mechanism mounted for a limited lost motion with respect tosaid shaft, said cam mechanism being arranged to operate saidmake-and-break means.

5. A reversible electric motor of the magnetic attraction type operatingon a make-and-break circuit comprising field poles, coil means formagnetizing said fleld poles, a main shaft, rotor poles fixed to saidmain shaft and rotatably positioned between said field poles, amake-andbreak device for alternately energizing and deenergizing saidcoil means, a notched collar loosely mounted on said main shaft, highand low cam surfaces on said collar, and a pin fastened to andprojecting radially from said main shaft, said pin and said notchedcollar cocam surfaces assume a different position with respect to saidshaft for clockwise rotation of said shaft than is assumed by said camsurfaces during counter-clockwise rotation of said shaft.

7. A reversible electric motor of the mmetic attraction type operatingon a make-and-break circuit comprising a set of two field poles, coilmeans for magnetizing said iield poles, a main shaft. a set of two rotorpoles fixed to said main shaft and rotatably positioned between saidfield poles, a make-and-break device for alternately energizing anddeenergizing said coil means. a notched collar loosely mounted on saidmain shaft, a set of two high and a set of two low cam surfaces on saidcollar, said high cam surfaces being spaced 180 apart and said low camsurfaces also beins spaced 180' apart, and a pinfastened to andprojecting radially from said assasos main shaft, said pin and saidnotched collar co-operating to provide limited lost motion for said camsurfaces.

8. A reversible electric motor comprising field poles, coil means formagnetizing said ileld poles, a main shaft, rotor poles fixed to saidshaft and rotatably positioned between said field poles, amake-and-break device for alternately energizing and deenergizing saidcoil means. and cam surfaces for opening and closing said make-andbreakdevice, said cam surfaces being mounted for a limited lost motion withrespect to said rotor. poles, whereby said cam surfaces assume adifferent position with respect to said rotor poles for clockwiserotation of said shaft than is assumed by said cam surfaces duringcounterclockwise rotation of said shaft.

WILLIAM T. BRENNAN.

